Production of lubricating oils

ABSTRACT

LUBRICATING OILS OF IMPROVED PROPERTIES ARE PREPARED BY TOPPING A CRUDE UNDER ATMOSPHERIC PRESSURE, DEASPHALTING THE REDUCED CRUDE, HYDROGENATING THE DEASPHALTED OIL AND DISTILLING THE HYDROGENATION PRODUCT UNDER REDUCED PRESSURE TO RECOVER LUBE OIL DISTILLATES. THE VACUUM RESIDMAY ALSO BE SOLVENT DEASPHALTED TO PRODUCE ADDITIONAL HEAVIER GRADE LUBRICANTS.

United States Patent U.S. Cl. 208-86 9 Claims ABSTRACT OF THE DISCLOSURE Lubricating oils of improved properties are prepared by topping a crude under atmospheric pressure, deasphalting the reduced crude, hydrogenatin g the deasphalted oil and distilling the hydrogenation product under reduced pressure to recover lube oil distillates. The vacuum residuum may also be solvent deasphalted to produce additional heavier grade lubricants.

This application is a continuation of application Ser. No. 774,481 filed Nov. 8, 1968, now abandoned.

This invention is concerned with the production of lubricating oils. More particularly, it is concerned with the production of lubricating oils of high viscosity index in goods yields. In one of its more specific embodiments, it is concerned with the production of high yields of SAE 20 grade lubricating oil.

In the refining of petroleum oils, the crude oil is customarily distilled at atmospheric pressure to remove naphtha, kerosene and light and heavy gas oils as distillate. The remaining atmospheric reduced crude is then subjected to distillation at reduced pressure, generally referred to as vacuum distillation, to yield as distillate vacuum gas oils which are customarily charged to catalytic cracking units and wax distillates which are subjected to further refining to make lubricating oils leaving as still residue a vacuum residuum. The vacuum residuum ordinarily is deasphalted and then solvent fractionated to recover heavy lube stocks and asphalt.

Varous procedural steps are available for the production of finished lubricating oils. Solvent refining with for example furfural, sulfur dioxide, dichloroethane, phenol and the like, is Ordinarily used as a means of removing cyclic compounds to increase the viscosity index. Acid treating is employed to improve the color stability and resistance to oxidation of the oil. Clay contacting is generally used as the final step to further improve the color and to remove residual traces of acid in the oil. Solvent dewaxing is used to lower the pour point of the oil.

In a typical operation, a crude oil is topped under atmospheric pressure to produce light distillates and an atmospheric reduced crude which is then vacuum distilled to produce lighter lube oils such as the SAE 10 and grades. The residue from the vacuum distillation is deasphalted and solvent fractionated to produce for example SAE 50 grade oil and cylinder stocks. These various fractions may then be further processed by solvent refining, solvent dewaxin g, acid treating and clay contacting.

Not all crude oils are suitable for processing into high quality paraffin base lubricating oils, that is, oils having a high viscosity index. Some properties which make for good lubricating-source crude oils are the presence of high VI hydrocarbons in the lube fractions, a high 3,725,245 Patented Apr. 3, 1973 yield of lube oil stocks from solvent refining and a high yield of SAE 20 grade oil relative to heavier or residual fractions since the SAE 20 requirements are greatest.

It is an object of the present invention to increase the content of high VI hydrocarbons in a given raw SAE grade as evidenced by a high viscosity index. A further object of the invention is to increase the percentage yield of the refined oil on solvent refining.

Another object is to shift the molecular weight distribution so as to increase the yield of SAE 20 oil and simultaneously reduce the yield of heavier oil. A further object is to increase the yield of high quality vacuum gas oil suitable for charging to catalytic: cracking. These and other objects will be obvious to those skilled in the art from the following disclosure.

I have now discovered a novel process for the production of improved lubricating oils in good yields. The process of my invention comprises topping a crude oil under substantially atmospheric pressure to produce an atmospheric reduced crude having a flash point, COC, of at least 300 F., deasphalting the resulting atmospheric reduced crude, subjecting the deasphalted oil to hydrogenation and vacuum distilling the hydrogenation product to produce a vacuum residuum and light lubricating oil distillate. In a more specific embodiment of the invention the residue from the vacuum distillation is subjected to deasphalting to yield additional lubricating oil fractions. In more specific embodiments light lubricating oils recovered as vacuum distillates and the oils recovered from the deasphalting are further refined by solvent refining and dewaxing.

Any hydrocarbon oil may be used as a charge stock to the process. Suitable crudes include those having a Watson characterization factor of at least 11.5 and preferably 11.8 or higher. This includes the so-called Intermediate Base and Paraflin Base crude oils which are customarily used in the manufacture of refined motor oils. The crude is charged to an atmospheric still and all material boiling up to about 700 F. including naphtha, kerosene and atmospheric gas oils is removed as distillate.

The atmospheric reduced crude is is then subjected to a deasphalting treatment. The deasphalting may be effected by contacting the atmospheric reduced crude with a deasphalting agent such as propane, normal butane, isobutane and mixtures thereof at a temperature in the range of 300 F., a dosage of 400-1000% and at pressures of about 200 to 600 p.s.i.g. Preferred conditions are temperatures of 275 F., dosages of 400-800% and pressures of 400-500 p.s.i.g. Advantageously, the temperature does not exceed the critical temperature of the solvent and the pressure is held somewhat above the autogenous pressure to prevent vaporization. This treatment results in an oil having a low asphalt content referred to as deasphalted oil and residue composed for the most part of asphalt.

The deasphalted atmospheric reduced crude or deasphalted oil which is a wide boiling range fraction containing vacuum gas oils and lubricating oil stocks is subjected to hydrotreating under relatively mild conditions including a temperature of 400800 F., a pressure between 250 and 1000 p.s.i.g., a space velocity between 0.25 and 3 v./v./hr. and a hydrogen rate of from 100-3000 s.c.f.b. Preferred conditions include a temperature of 500-650 F a presure of 300-800 p.s.i.g., a space velocity between 0.5 and 1.5 and a hydrogen rate between 1000 and 2500 s.c.f.b.

The conditions are selected so that there is little, if any, conversion to materials boiling below the gas oil range. Advantageously the product liquid yield from the hydrotreating step is not less than about 95 volume percent basis charge to the hydrorefining reaction zone.

Suitable hydrotreating catalysts for use in the process comprise metals or compounds of metals of Grou VI and Group VIII of the Periodic Table. Non-limiting examples of such components are chromium, molybdenum, tungsten, iron, cobalt, nickel and mixture thereof and noble metals such as platinum and palladium or compounds thereof. Generally these components are supported on a base comprising a refractory inorganic oxide material such as alumina, silica, magnesia, zirconia, titania and the like and mixtures thereof. The support should have little, if any, cracking activity. The catalyst may be used in the form of a slurry, a fixed bed, or a fluidized bed. When used in the form of a fixed bed, the flow may be either upward or downward or the flow of hydrogen may be countercurrent to the flow of oil. Particularly suitable catalysts are those containing from 2-10% cobalt or nickel or 530% molybdenum or tungsten. Preferred catalysts are those containing about 6% nickel and 20% tungsten or about 2- 4% cobalt or nickel and 5-10% molybdenum supported on alumina. Although the catalyst may be subjected to chemical change in the reaction zone due to the presence of sulfur and hydrogen therein, the catalyst is ordinarily in the form of the oxide or sulfide when first brought into contact with the charge stock.

The hydrogen used in the hydrotreating step need not be pure hydrogen. Satisfactory results may be obtained with hydrogen containing as much as 30-40% impurities. Suitable sources of hydrogen are catalytic reformer byproduct hydrogen and hydrogen produced by the partial combustion of a hydrocarbon material followed by shift conversion and scrubbing.

After the hydrotreating step and the separation of hydrogen from the reaction zone effluent, the hydrotreated deasphalted atomspheric reduced crude is subjected to vacuum distillation to remove as distillate vacuum gas oils and lube oils of SAE 10 and SAE grades. Advantageously, the residue from the vacuum distillation can be treated with a deasphalting agent and SAE 50 grade oil and cylinder stocks recovered. This second deasphalting step may be conducted at different conditions than the deasphalting of the atomspheric reduced crude. Dosage in the range of 500-1000% may be used at temperature between about 120 and 300 F. and pressures between about 250 and 900 p.s.i.g. Suitable deasphalitng agents, as in the first deasphalting step, include propane, normal butane, isobutane and mixtures thereof.

For solvent refining of the various lube oil fractions, various solvents such as furfural, phenol, dichloroethane, sulfur dioxide and the like may be used. A particularly suitable solvent is N-methyl pyrrolidone. The solvent refining is effected at dosages of 100-600% and temperatures of 100-250 F. Preferred conditions are a dosage of 100 300% and a temperature of 100-180 F. N-methyl pyrrolidone is a particularly desirable solvent in that it may be used at a lower dosage than the other solvents and yet the final product has better color.

Dewaxing, to lower the pour point of the oil, may be effected by contacting the solvent refined oil with a dewaxing agent such as a mixture of a ketone such as acetone, methyl ethyl ketone or n-butyl ketone and an aromatic solvent such as benzene or toluene in a ratio of about 3-4 parts by volume of solvent per part of oil, cooling the mixture to a temperature close to the desired pour point of the finished oil and removing the Waxy components by filtering or centrifuging. The dewaxed oil is then subjected to flash distillation and stripping to remove residual solvent.

Alternatively, the solvent refined oil may be dewaxed by contacting the oil in the presence of hydrogen with a catalyst comprising a hydrogenation component such as that used in the hydrotreating catalyst supported on a decationized mordenite. Preferably the support is prepared by treating a synthetic mordenite with acid to replace the sodium ions with hydrogen ions and the hydrogenating component comprises a noble metal such as platinum or palladium. Advantageously, the synthetic mordenite is treated with acid to the extent that a portion of the alumina is leached out to produce a mordenite of increased silica:alumina ratio and increased dewaxing activity. The catalytic dewaxing may be carried out at a temperature of 450 to 950 F a pressure of atmospheric to 5000 p.s.i.g., a space velocity of 0.1 to 10 liquid volumes per hour per volume of catalyst and a hydrogen rate of 020,000 s.c.f. per barrel. Preferred conditions are 500 to 850 'F., 200 to 1500 p.s.i.g., 0.25 to 5.0 v./v./hr. and SOD-10,000 s.c.f.b.

The following examples which are presented for illustrative purposes only show that by my novel process higher yields of valuable high quality cracking charge stock, higher yields of the most desirable SAE 20 grade oil and improved response to solvent refining are obtained.

EXAMPLE I This example represents the conventional processing of the prior art. The charge is an atomspheric reduced Safaniya crude having the following characteristics:

TABLE 1 Yield basis crude, vol. percent 63.5 Gravity, API 15.2 Flash, COC, F 320 Viscosity, SUS, 210 F. 300 Watson Characterization Factor 11.7

Yields and properties of the SAE 10 and SAE 20 oils from vacuum distillation and the SAE 50 and cylinder stock by deasphalting the vacuum residuum using isobutane at a dosage of 800%, a temperature of 292 F. and a pressure of 740 p.s.i.g. are shown in Table 2.

TABLE 2 SAE Cyl.

10 20 50 stock Yield basis crude, volume percent 3. 8 7. 7 6. 3 9. 8 Gravity, API 23. 5 21. 5 22.3 17. 0 Flash, COO, F 395 460 540 575 V scosity, SUS, 210 F 43.1 55. 4 94. 7 314 Viscosity index 72 62 81 76 EXAMPLE II temperautre of 195 F. and a pressure of 545 p.s.i.g. and

recovering SAE 50 grade oil and deasphalting the residue with propane at 800% dosage, 120 F. and 250 p.s.i.g. and recovering cylinder stock.

Although the hydrogenation yield is substantially volume percent, indicating little conversion to materials lighter than the charge, there is a considerable increase in yield in Example II of the more valuable SAE 10 and 20 oils over Example I. The vacuum gas oil obtained in this example is also a much more valuable cracking charge stock than that obtained in Example I.

Table 4 shows the yields in volume percent of various fractions from Examples I and 11 basis crude.

TABLE 4 I II Vacuum gas oil 13. 16. 0 SAE 10 3. 8 5.0 7. 7 B. 0

D. A. residue 22.9 20. 4

Examples I and II show the superiority of my process which involves deasphalting an atmospheric reduced crude and hydrogenating the deasphalted oil prior to vacuum distilling over conventional processing in which the atmospheric reduced crude is subjected to vacuum distillation and the bottoms deasphalted.

EXAMPLE III In this example the charge is an atmospheric reduced Safaniya crude having the following characteristics:

TABLE 5 Yield basis crude, volume percent 70.0 Gravity, API 14.9 Flash, COC, F. 310 Viscosity, SUS, 210 F. 169.4 Viscosity Index 81 Watson Characterization Factor 11.53

Yields and product characteristics from deasphalting the charge with iso-butane at a dosage of 800%, a temperature of 240 F. and a pressure of 475 p.s.i.g. and vacuum distilling to recover SAE and SAE grade oils are shown below in Table 6.

TABLE 6 SAE Yield basis crude, volume percent 4. 0 7. 0 Gravity, API 24. 3 21. 0 Flas GOG, F 410 490 Viscosity, SUS 210 F.. 48. 4 57. 3 Viscosity index 75 62 The vacuum gas oil yield amounts to 14.5 volume percent basis crude.

EXAMPLE IV TABLE 7 SAE Yield basis crude, volume percent 3. 5 8. 5 Gravity, API"... 26.0 23. 7 Flash, 000, F 430 470 Viscosity, SUS, 210 F 43.1 57. 4 Viscosity index 78 72 The vacuum gas oil yield amounts of 176 volume percent basis crude. This material is a superior charge stock for catalytic cracking.

6 EXAMPLE v This example shows that in my novel process there is better response to solvent refining than in conventional processing. Columns 1, 2, 3 and 4 in Table 8 give the data on the finishing of the SAE 10 and SAE 20 oils from Example III and the SAE 10 and SAE 20 oils from Example IV respectively.

TABLE 8 Solvent refining:

olvent 1 N MP NMP NMP N MP Dosage, percent I 125 100 100 Temperature, F 130 130 130 130 Refined oil yield, vol. percent. B6. 5 61. 7 69. 5 70. 0 Refined oil:

Gravity, API 20. 8 32. 9 20. 8 Flash, COG, F 385 405 400 400 Viscosity, SUS, 210 F- 41. 9 49. 2 42. 7 50. 3 Viscosity index 106 106 Solvent dewaxing (MEK-toluene):

Dilution 3:1 3:1 3:1 3:1 Wash 2.521 2.521 2.521 2.5:1 Dewaxing temperature, F -15 -15 15 15 Percent MEK in solvent- 50 50 50 50 1 N MP N methy1 2-pyrrolidone.

Table 9 below shows the yields of various fractions from Examples III and IV basis volume percent of the crude.

Examples III, IV and V show that the superiority of my process is due to the sequence in Example IV where the atmospheric reduced crude is deasphalted and the deasphalted oil hydrotreated and then vacuum distilled. Merely disasphalting the atmospheric reduced crude and vacuum distilling the deasphalted oil as in Example III does not yield the improved results obtained in my process.

Obviously, various modifications of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and therefore, only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. A process for the production of lubricating oils which comprises topping a crude oil under substantially atmospheric pressure up to a temperature of about 700 F. to produce an atmospheric reduced crude con sisting of vacuum gas oils, lubricating oils and a vacuum residuum, deasphalting the resulting atmospheric reduced crude using a deasphalting agent consisting essentially of a hydrocarbon solvent, subjecting the deasphalted oil so produced to mild catalytic hydrogenation at a pressure between about 300 and 800 p.s.i.g., a temperature between about 500 and 650 F., a space velocity between about 0.5 and 1.5 v./v./hr. and a hydrogen rate between about 1000 and 2500 s.c.f.b. to obtain a vacuum gas oil and heavier hydrogenation product liquid yield of not less than 95 volume percent basis charge to the hydrogenation zone, and vacuum distilling the hydrogenation product to produce a vacuum residuum and a lubricating oil distillate.

2. The process of claim 1 in which the hydrogenation is conducted in the presence of a catalyst comprising cobalt and molybdenum.

3. The process of claim 1 in which the hydrogenation is carried out in the presence of a catalyst comprising nickel and molybdenum.

4. The process of claim 1 in which the lubricating oil distillate is subjected to solvent refining.

5. The process of claim 4 in which the solvent is furfural.

6. The process of claim 4 in which the solvent is N- methyl-2-pyrol1idone.

7. The process of claim 4 in which the solvent refined lubricating oil is subjected to a dewaxing treatment.

8. The process of claim 1 in which the deasphalting agent comprises propane.

9. The process of claim 1 in which the deasphalting agent comprises isobutane.

8 References Cited UNITED STATES PATENTS 1/ 1968 Egan et al. 208--18 12/1968 Campagne 208-18 2/1937 Tuttle 208-18 12/1966 Biribauer et a1 208-309 1/1968 Szepe et a]. 208-86 11/1960 Beuther et a1. 20819 HERBERT LEVINE, Primary Examiner U.S. Cl. X.R. 

